ftp.xmission.com/2014.06.ftp.xmission.com.tar/ftp.xmission.com/pub/lists/fractdev/archive/fractdev.200109

Internet Message Format | 2001-09-29 | 20KB

From: "Scott D. Boyd" <[e-mail]>
Subject: (fractdev) Speed of Xfractint vs Fractint
Date: 12 Sep 2001 12:13:52 -0500

Jonathan and/or Tim,

I don't know if you are aware of this, but there is a HUGE speed diff=
erence=20
between Xfractint and Fractint when calculating floating-point fracta=
ls.=20
(Probably any fractals, for that matter, since Xfractint is always in=
=20
floating-point mode.)

I hadnoticed a speed differnce for quite some time when generating Ji=
m Muth's=20
FOTD images. I had thought for quite awhile that it was because of my=
 450Mhz=20
AMD K6-2 CPU, which I hear is a real slacker on floating-point calcul=
ations.=20
So, I recently bought a 900Mhz Athlon CPU, and ran Jim's FOTD of 9-1-=
01 for a=20
comparison of the "speed improvement".=20

Paul N. Lee had posted an email on Sept. 2 with some comparison times=
 for=20
that fractal:

=A0 =A0 Jim's P200 at SF5 =A0 =A0 =A0 =A001:45:19.72=20
=A0 =A0 Scott's machine at SF5 =A0 03:53:39.68  (this was with my 450=
 Mhz K6-2)
=A0 =A0 Paul's old P700 at SF5 =A0 =A0 =A0 00:32:20.19=20

(Keep in mind that both Jim and Paul use Fractint, I'm of course usin=
g=20
Xfractint.)

When I generated the fractal on my 900 MhzAthlon, the time decreased =
to=20
approx.  1 hr - 23 mins. I thought "this is terrible! It's *still slo=
wer*=20
than Paul's P700!". When I exited to the Linux command-line, and gene=
rated=20
the fractal using the "-disk" option, it only saved a couple of minut=
es. Then=20
I swapped in a Win95 HD to my Athlon box, booted to the DOS prompt, a=
nd=20
generated the fractal using Fractint v20.0. The generation time dropp=
ed to a=20
mere 19 minutes, 54.30 seconds!! That's an almost 80% decrease in=
=20
generation-time!

I'm not expecting this to be fixed, as I imagine the problem probably=
 lies in=20
the algorithms used in Xfractint. I don't know - the math used in cre=
ating=20
fractals is *way* beyond me... I just wanted ya'll to be aware of it.

Until later,
Scott


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-------------------------------------------------------------------------------

From: Tim Wegner <[e-mail]>
Subject: Re: (fractdev) Speed of Xfractint vs Fractint
Date: 12 Sep 2001 17:40:40 -0600

Scott wrote:

> I don't know if you are aware of this, but there is a HUGE speed > > difference
> between Xfractint and Fractint when calculating floating-point fractals.
> (Probably any fractals, for that matter, since Xfractint is always in
> floating-point mode.)

It makes a big difference what fractal type is being used. Quite a number of the built-in fractal
types have dedicated hand-optimized assembler code. This is not used in Xfractint.

The debugflag=90 switch forces fractint to use the C rather than the assembler. A fairer
comparison between Fractint and Xfractint would be to generate the fractal using fractint with the
debugflag=90 switch.

It might not be too bad to incorporate some assembler into the intel Linux version, but so far no
one has taken up that project. Whoever did this who need to know how tro migrate medium
memory model assembler to a flat memory model.

Jonathan knows more about this since he wrote some of the assembler speedups.


> I'm not expecting this to be fixed, as I imagine the problem probably lies in
> the algorithms used in Xfractint. I don't know - the math used in creating
> fractals is *way* beyond me... I just wanted ya'll to be aware of it.

It's not really the algorithms, but C vs assembler.

The parser in Fractint also has been written fairly efficiently, so formula fractals are also faster
under Fractint than Xfractint. This is one of the reasons we have held onto the DOS version of
Fractint for so long.

maybe we should make a fractint-optimized MSDOS floppy boot image. Then Fractint could live
forever :-)

Does anybody know if Fractint runs under Windows XP? I expect it does, but with some video
limitations. I am not planning to "upgrade".

Tim


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-------------------------------------------------------------------------------

From: "Paul N. Lee" <[e-mail]>
Subject: Re: (fractdev) Speed of Xfractint vs Fractint
Date: 12 Sep 2001 18:35:55 -0500

Tim Wegner wrote:
>
> Does anybody know if Fractint runs
> under Windows XP?  I expect it does...

According to an article yesterday from AnchorDesk, Mark Croft (lead
product manager for the Windows XP group at Microsoft) says the
following concerning DOS apps running under XP:

     "Several improvements to the DOS virtual machine were
      made in Windows XP to ensure broader compatibility
      with many popular DOS titles--specifically, new
      SoundBlaster 16 support and a number of quality fixes.
      We tested a number of popular DOS titles to ensure
      improved compatibility over Windows 2000 and NT4"

And concerning drivers:

     "Microsoft is providing a tool--Upgrade Advisor (UA)--
      which users can run on their machines prior to
      installing Windows XP to determine how compatible
      their systems will be with Windows XP.  This tool
      can be updated dynamically via a Web connection and
      provides an easy way to check a whole PC.  The data
      on this is identical to the data used by Windows Setup
      during an upgrade."

Sincerely,
P.N.L.
http://www.fractalus.com/cgi-bin/theway?ring=fractals&id=43&go

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-------------------------------------------------------------------------------

From: Tim Wegner <[e-mail]>
Subject: (fractdev) (Fwd) bug in fractint 20.1.13?
Date: 17 Sep 2001 18:05:50 -0600

I received this email today:

Hi,

here is my bug report:

In formula interpreter, rand/srand does not work as it apparently
should. This applies to Fractint 20.0 under DOS, under Linux, and
20.1.13 under Linux. -- First, the formula translator generates a
segfault when compiling a formula with no parameters.  Serge Then
consider the following two formulae: test1 generates the correct
picture, while test2 does not. The difference between test1 and test2 is
only in the implementation of rand and srand(): in test1 we have our own
implementation, and in test2 we use rand and srand(). Apart from the
visual difference, it seems that test2 does not zoom correctly while
test1 does. This seems to indicate that srand() and rand are somewhat
broken. I could not determine where the bug is in the code, but, apart
from that, it does seem likely that the rand routine is not a very high
quality random number generator. The one I used below is also not very
good, it is just something that is quick to implement.

Best regards,

--
    Serge

test1 { ; srand doesn't seem to work as expected, so we make our own rand
; build a random fractal pattern of squares
        z=0, p = pixel/32, v=real(p1)+15887, A=real(32767), B=137, C=2997 :
        p = p*2, p = p - floor(p)  ; blowup, now both re and im(p) are between 0 and 1
        ; now we need to generate the random number for this quadrant
        v=v*B+C, v=v-A*floor(v/A)
        IF( (real(p)<0.5) && (imag(p)<0.5) )
                v=v*B+C, v=v-A*floor(v/A), ENDIF
        IF((v/A)<0.5+imag(p1)), z=z+1, ELSE, z=z-0.001, ENDIF ; exit with fixed probability
        real(z) <= 5 }

test2 { ; srand doesn't seem to work as expected
; build a random fractal pattern of squares
        z=0, p = pixel/32, srand(real(p1)) :
        p = p*2, p = p - floor(p)  ; blowup, now both re and im(p) are between 0 and 1
        ; now we need to generate the random number for this quadrant
        v=rand
        IF( (real(p)<0.5) && (imag(p)<0.5) )
                v=rand, ENDIF
        IF(v<0.5+imag(p1)), z=z+1, ELSE, z=z-0.001, ENDIF ; exit with fixed probability
        real(z) <= 5
}

------- End of forwarded message -------

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-------------------------------------------------------------------------------

From: "Jonathan Osuch" <[e-mail]>
Subject: Re: (fractdev) (Fwd) bug in fractint 20.1.13?
Date: 17 Sep 2001 20:25:04 -0500

Tim,

> In formula interpreter, rand/srand does not work as it apparently
> should.

That doesn't surprise me.  I think we truncate the random numbers so that
floating point images look the same as integer images (when random numbers
are used).

Any takers on looking into this?

Jonathan



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-------------------------------------------------------------------------------

From: "Jonathan Osuch" <[e-mail]>
Subject: Re: (fractdev) Speed of Xfractint vs Fractint
Date: 17 Sep 2001 20:31:10 -0500

> It might not be too bad to incorporate some assembler into the intel Linux
version, but so far no
> one has taken up that project. Whoever did this who need to know how tro
migrate medium
> memory model assembler to a flat memory model.

> Jonathan knows more about this since he wrote some of the assembler
speedups.

I've looked briefly into this.  One of the problems is the syntax of the
commands is reversed so that each line of code will have to be changed.

I doubt the formula parser will get translated due to its extensive use of
macros.  The mandelbrot code could be changed in a reasonable amount of
time.  I've been wanting to do a major change to the periodicity checking
code to check the magnitude instead of X and Y.  Although this seems like
rambling, the periodicity checking code is part of the assembly code that
will need to be converted.

The major problems are too much to do and not enough time.  Being tired all
the time doesn't help either.

I need to finish up my latest patch, which will appear as version 20.2 for
backwards compatibility reasons.  Maybe this coming weekend.

Jonathan




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-------------------------------------------------------------------------------

From: "Jonathan Osuch" <[e-mail]>
Subject: Re: (fractdev) (Fwd) bug in fractint 20.1.13?
Date: 27 Sep 2001 20:20:54 -0500

Tim,

> In formula interpreter, rand/srand does not work as it apparently should.

I've looked at this and there are several points of note.  He is assuming
that every time you make an assignment from the rand variable its value has
changed.  This is false.  The only time rand gets changed is when srand() is
called.

It appears that the string of psuedo-random numbers he is using starts over
at the start of the calculation for each pixel.  Our psuedo-random string
should do this also if the initial srand call is srand(seed) and any
subsequent calls are srand(rand).  After rearranging his second formula, it
still doesn't work like his first one.

The srand() routine depends on the integer math argument variables getting
set.  Since we have to use the floating point math so that the if-then logic
will work, the integer values may not be getting set.

Jonathan



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From: "Jonathan Osuch" <[e-mail]>
Subject: (fractdev) Latest patch
Date: 27 Sep 2001 20:28:00 -0500

Tim,

I uploaded patch 2002p00.zip to the fractint directory.  Please take a look
at it.  Specifically, see if you want to change any of the words in the doc
file concerning the move from CompuServe to the web.  Thanks.

I'll supply a source sync once this patch is official.

Jonathan



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From: Tim Wegner <[e-mail]>
Subject: Re: (fractdev) Latest patch
Date: 27 Sep 2001 21:28:13 -0600

> I uploaded patch 2002p00.zip to the fractint directory.  Please
> take a look at it.  Specifically, see if you want to change any of > the words in the doc file
concerning the move from CompuServe to
> the web.  Thanks.

Will look at it on Saturday (going out Friday night). Thanks!

Sheesh - Compuserve - ancient history :-)

Tim


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From: Tim Wegner <[e-mail]>
Subject: Re: (fractdev) Latest patch
Date: 29 Sep 2001 10:56:38 -0600

>
> I uploaded patch 2002p00.zip to the fractint directory.  Please take a look
> at it.  Specifically, see if you want to change any of the words in the doc
> file concerning the move from CompuServe to the web.  Thanks.

Your edits are a big improvement over that horribly obsolete language that was there before.
Thanks! Let's make your patch official.

I'll look to see if more updating can be done, but there is no reason to delay your patch.

Tim


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From: "Damien M. Jones" <[e-mail]>
Subject: Re: (fractdev) Latest patch
Date: 29 Sep 2001 12:54:51 -0400

Hey gang,

As you probably noticed, my server went offline Thursday for several hours.
I was moving it to its new host... finally. And because this new host isn't
paranoid about network security (they're a co-location service provider,
their attitude is that the security of my box is my business, not theirs)
I'll be able to re-activate some things that had been disabled. Things like
anonymous FTP, and moving SSH back to its normal port. Right now I'm trying
to catch up on all the stuff that hasn't been done over the past few weeks,
but I wanted to let you know that I'm not dropping off the face of the
earth (and neither is the server).

Damien M. Jones   \\
[e-mail]  \\  Fractalus Galleries & Info:
                    \\  http://www.fractalus.com/

Please do not post my e-mail address on a web site or
in a newsgroup.  Thank you.


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From: Tim Wegner <[e-mail]>
Subject: Re: (fractdev) Latest patch
Date: 29 Sep 2001 12:15:04 -0600

Damien wrote:

> As you probably noticed, my server went offline Thursday for
> several hours.
> I was moving it to its new host... finally.

I didn't notice. A few hours ago I was able to FTP in to get Jonathan's patch (obviously, using my
account, not anonymous FTP).

> And because this new host isn't
> paranoid about network security (they're a co-location service provider,
> their attitude is that the security of my box is my business, not theirs)
> I'll be able to re-activate some things that had been disabled. Things like
> anonymous FTP, and moving SSH back to its normal port.

Thanks, just let us know the status as it changes.

Tim


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From: "Jonathan Osuch" <[e-mail]>
Subject: Re: (fractdev) Latest patch
Date: 29 Sep 2001 20:57:38 -0500

Tim,

> I'll look to see if more updating can be done, but there is no reason to
delay your patch.

Okay, I'll post it officially in the morning (when I'm not tired).

Thanks.

Jonathan



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From: "Jonathan Osuch" <[e-mail]>
Subject: Re: (fractdev) Latest patch
Date: 30 Sep 2001 09:10:19 -0500

Damien,

> As you probably noticed, my server went offline Thursday for several
hours.
> I was moving it to its new host... finally. And because this new host
isn't
> paranoid about network security (they're a co-location service provider,
> their attitude is that the security of my box is my business, not theirs)
> I'll be able to re-activate some things that had been disabled.

I am unable to ftp the version 20.2 files to the server.  Help!  I thought
it might be a Zone Alarm problem, but shutting it down and trying again
didn't help.

Jonathan





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From: Tim Wegner <[e-mail]>
Subject: Re: (fractdev) Latest patch
Date: 30 Sep 2001 13:10:01 -0600

Jonathan wrote:

> I am unable to ftp the version 20.2 files to the server.  Help!  I thought
> it might be a Zone Alarm problem, but shutting it down and trying again
> didn't help.

I am having the same problem, can't upload. I do seem to be able to download. Also, pscp is not
working for me right now either.

Tim


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